This application claims benefit of Japanese Application No. 2000-211575 filed in Japan on Jul. 12, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to an endoscope, or more particularly, to an endoscope having an insertion member that includes a flexible tube, and capable of being autoclaved (sterilized with high-temperature high-pressure steam).
2. Description of the Related Art
In the medical field, endoscopes are widely adopted these days. The endoscope has an elongated insertion member thereof inserted into a body cavity in order to observe a deep region in the body cavity, or has, if necessary, a therapeutic accessory passed through it in order to perform a cure or treatment. As for the medical equipment, it is essential to thoroughly disinfect or sterilize the used endoscope.
Recently, autoclaving (high-temperature high-pressure steam sterilization) has come to be a mainstream of sterilization of endoscope equipment. This is attributable to the fact that autoclaving is less labor-intensive, renders the endoscope usable immediately after completion of sterilization, and is less expensive.
Typical regulations for autoclaving are stipulated in the standard ANSI/AAMI ST37-1992 approved by the American National Standards Institute (ANSI) and published from the Association for the Advancement of Medical Instrumentation (AAMI). According to the standard, a pre-vacuum sterilization process should be performed at 132xc2x0 C. for 4 minutes and a gravity settling sterilization process should be performed at 132xc2x0 C. for 10 minutes.
The environmental conditions for autoclaving are quite severe for endoscopes. For realizing an endoscope that meets the environmental conditions and that is so durable as to be autoclaved, various measures must be taken against high pressure, high temperature, and steam unlike realization of an endoscope that is reusable only after disinfected or sterilized according to any other means. In particular, an insertion member of the endoscope that is inserted into a patient""s body is required to offer various delicate properties including flexibility and resiliency. Because the insertion member tends to be more susceptible to high pressure, high temperature, and steam than a distal rigid part (the properties of the insertion member are likely to be degraded), more sophisticated measures must be taken in relation to the insertion member.
As described, for example, in Japanese Unexamined Patent Application Publication No. 2-283346, a conventional endoscope capable of being autoclaved has an elongated insertion member that includes a flexible tube composed of a spiral tube, a braid, and a sheathing layer. The spiral tube has a metallic belt wound spirally. The spiral tube is sheathed with the braid, and the braid is sheathed with the sheathing layer that is made of a resin.
However, as far as the endoscope described in the Japanese Unexamined Patent Application Publication No. 2-283346 is concerned, when the endoscope is sterilized using an autoclave (a high-temperature high-pressure steam sterilizer), the sheathing of the flexible tube of the insertion member gets harder. This is because the sheathing is thermally loaded during high-temperature high-pressure steam sterilization. The flexural rigidity of the flexible tube, that is, the ratio of force applied to a predetermined length in longitudinal directions of the flexible tube to a magnitude of bend of the length gets higher. Consequently, the whole insertion member is hardened.
Moreover, a user does not expect that the hardness of the flexible tube attained after sterilization with high-temperature high-pressure steam gets higher than it originally is before the sterilization. If the user uses the endoscope in the same manner as he/she does before the flexible tube gets harder, the user may fail to insert the insertion member into the large intestine or the like such as a tortuous intracavitary organ having many bent parts. Otherwise, if the flexural rigidity of the flexible tube gets lower than the original flexural rigidity, there is a fear that maneuverability may somewhat deteriorate. Nevertheless, the insertion member can be advanced smoothly through the large intestine or any other tortuous organ.
The present invention attempts to break through the current foregoing situation. An object of the present invention is to provide an endoscope having the inserting smoothness of an insertion member thereof optimized. That is to say, the endoscope is designed so that the flexural rigidity of a flexible tube attained after sterilization with high-temperature high-pressure steam will be equal to or lower than the flexural rigidity thereof attained before the sterilization.
According to the first aspect of the present invention, there is provided an endoscope having an insertion member that includes a flexible tube having a spiral tube, which is formed by spirally winding a metallic bent, sheathed with a braid and having the braid sheathed with a sheathing made of a resin.
In the endoscope, the flexural rigidity of the flexible tube of the insertion member attained at a predetermined position at the room temperature after the flexible tube is loaded during high-temperature high-pressure steam sterilization is equal to or lower than the flexural rigidity attained before the flexible tube is loaded.
Owing to the foregoing constituent feature, the flexural rigidity of the flexible tube attained after sterilization with high-temperature high-pressure steam is equal to or lower than the flexural rigidity thereof attained before the sterilization. This results in the endoscope having the inserting smoothness of the insertion member optimized.
According to the second aspect of the present invention, there is provided an endoscope in which the hardness of a resin sheathing of a flexible tube attained at the room temperature after the sheathing is loaded during high-temperature high-pressure steam sterilization is equal to or lower than the hardness thereof attained before the sheathing is loaded.
According to the third aspect of the present invention, there is provided an endoscope in which when a flexible tube contracts in longitudinal directions at the room temperature after loaded during high-temperature high-pressure steam sterilization, even if the flexible tube is held bent by a predetermined magnitude of bend at the room temperature after loaded during high-temperature high-pressure steam sterilization, the adjoining belt portions of a spiral tube of the flexible tube do not come into contact with one another.
According to the fourth aspect of the present invention, there is provided an endoscope capable of being sterilized with high-temperature high-pressure steam at the temperature ranging from substantially 115xc2x0 C. to substantially 140xc2x0 C. at a loading step.
According to the fifth aspect of the present invention, there is provided an endoscope in which the resin sheathing of a flexible tube thereof is made of a resin of either an ester-series thermoplastic elastomer or an amide-series thermoplastic elastomer.